A Distributed Antenna System (DAS) utilizes a plurality of distributed antennas connected to a single base station in a wired manner or through a dedicated line. The base station includes a plurality of antennas which is distributed and located in a cell for providing a service. The DAS is different from a Centralized Antenna System (CAS), in which a plurality of base station antennas is provided at the center of a cell, in that a plurality of antennas is distributed and located so as to be spaced apart from one another by a predetermined distance in a cell. The CAS is generally a cellular communication system such as a Wideband Code Division Multiple Access (WCDMA), High Speed Packet Access (HSPA), Long Term Evolution (LTE)/Long Term Evolution-Advanced (LTE-A) or 802.16 system, and utilizes various multiple antenna schemes, in which multiple antennas are mounted in a single base station in a cell-based structure, such as an Open Loop-Multi Input Multi Output (MIMO) scheme, a Closed Loop-MIMO scheme or a Multi-BS MIMO scheme.
The DAS is different from a femto cell in that each distributed antenna unit does not directly manage an antenna region thereof, but the base station located at the center of the cell manages all distributed antenna regions located in the cell. In addition, the DAS is different from a multi-hop type relay system or an ad-hoc network, in which a base station and a Relay Node (RN) are wirelessly connected, in that the distributed antenna units are connected in the wired manner or through the dedicated line. In addition, the DAS is different from a repeater structure for amplifying a signal and transmitting the amplified signal in that each distributed antenna can transmit different signals to User Equipments (UE) adjacent to the antenna according to a command of the base station.
Such a DAS may be considered a MIMO system because the distributed antennas simultaneously transmit and receive different data streams so as to support a single UE or multiple UEs. From the viewpoint of the MIMO system, in the DAS, since the antennas are distributed at various positions in the cell, a transmission region of each antenna is reduced compared with the CAS, thereby reducing transmit power. In addition, the transmission distance between the antenna and the UE is reduced so as to reduce path loss and to increase data transfer rate. Therefore, it is possible to increase transmission capacity and power efficiency of a cellular system and to satisfy communication performance with relatively uniform quality regardless of the position of a user in the cell, as compared with the CAS. In addition, since the base station and the plurality of distributed antennas are connected in the wired manner or through the dedicated line, signal loss is low, correlation and interference between antennas are reduced, and a Signal-to-Interference plus Noise Ratio (SINR) is high.
The DAS may be utilized in parallel with the existing CAS or may replace the CAS so as to establish a new cellular communication standard, in order to reduce costs necessary for installing more base stations in a next-generation mobile communication system and costs necessary for maintaining a backhaul network, to enlarge service coverage and to improve SINR.
However, until now, no research has been conducted into an apparatus and method for controlling inter-cell interference in a multi-cell environment, to which the DAS is applied.